If you would like to authorize someone to use your garage, here is a sample authorization letter to use a garage.
To [Recipient name]
Dear, [Reciepient name]
This letter is to verify that I, [Your name] have authorized my brother, [Brother’s name] to use the garage on [Date] from [Start time] to [End time].
I will not be available on the given date as I have other business to attend to. However, my brother has the authorization to sign any documents, if required, on my behalf. Any inconvenience caused by this is regretted.
Thanking you for your cooperation.